The present invention relates in general to devices and methods for endoscopic dissection of a blood vessel within the limb of a patient, and, more specifically, to an insufflation device for maintaining a steady volume around an endoscope for better visualization within a surgical tunnel formed around the blood vessel to be dissected/harvested.
In connection with coronary artery bypass grafting (CABG), a blood vessel or vessel section, such as an artery or vein, is “harvested” (i.e., removed) from its natural location in a patient's body to use it elsewhere in the body. In CABG surgery, the blood vessel is used to form a bypass between an arterial blood source and the coronary artery that is to be bypassed. Among the preferred sources for the vessel to be used as the bypass graft are the saphenous veins in the legs and the radial artery in the arms.
Endoscopic surgical procedures for harvesting a section of a vein (e.g., the saphenous vein) subcutaneously have been developed in order to avoid disadvantages and potential complications of harvesting through a continuous incision. One such minimally-invasive technique employs a small incision for locating the desired vein and for introducing one or more endoscopic harvesting devices. Primary dissection occurs by introduction of a dissecting instrument through the incision to create a working space and separate the vein from the surrounding tissue. Then a cutting instrument is introduced into the working space to sever the blood vessel from the connective tissue and side branches of the blood vessel. The branches may be cauterized using the cutting instrument.
In one typical procedure, the endoscopic entry site is located near the midpoint of the vessel being harvested, with dissection and cutting of branches proceeding in both directions along the vessel from the entry site. In order to remove the desired section of the blood vessel, a second small incision, or stab wound, is made at one end thereof and the blood vessel section is ligated. A third small incision is made at the other end of the blood vessel section which is then ligated, thereby allowing the desired section to be completely removed through the first incision. Alternatively, only the first two incisions may be necessary if the length of the endoscopic device is sufficient to obtain the desired length of the blood vessel while working in only one direction along the vessel from the entry point.
An example of a commercially available product for performing the endoscopic vein harvesting described above is the VirtuoSaph Plus™ Endoscopic Vein Harvesting System from Terumo Cardiovascular Systems Corporation of Ann Arbor, Mich. An endoscopic vein harvesting system of this type is also shown in U.S. Pat. Nos. 7,331,971 and 8,048,100 and U.S. patent application publications 2010/0292533 and 2012/0035606, which are incorporated herein by reference in their entirety.
The dissector tool typically comprises a longitudinal stainless steel or plastic rod with a tip at one end and an operator handle at the other. The tip is tapered to a blunt end and is made of transparent plastic. An endoscope including an optical cable is inserted through the hollow handle and hollow rod to abut the tip to allow for endoscopic viewing during dissection. The dissection proceeds along the perimeter of the vein being harvested to separate it from the surrounding tissue and to expose the side branches of the vein so that they can be severed with the cutting tool.
During dissection and cutting, an insufflation gas such as carbon dioxide is introduced to the subcutaneous space surrounding the blood vessel to improve visualization of the tissue structures within the operative tunnel being created around the vessel. The ability of the tunnel to be inflated is facilitated in part by the use of a trocar at the entry site to provide a partial seal around the endoscopic instrument. Since there is not a 100% trocar seal by design, a continuous supply of the insufflation gas is provided through the endoscopic instrument to be expelled distally at its tip.
The insufflation gas is typically provided by a regulated source known as an insufflation device using a gas cylinder or a pipeline installed in a hospital setting. A target gas flow is set by the clinician, but the flow is normally modulated in order to ensure that a predetermined gas pressure is not exceeded within the surgical tunnel. As a result of turning the gas flow on and off by the insufflation device to avoid over-pressurizing the site while attempting to maintain a sufficient opening of the tunnel, partial pulsations in the insufflation can become evident in the tunnel along with corresponding changes in the visible volume of the tunnel. Consequently, distracting pulsations can sometimes occur in the endoscopic view as seen by the clinician.